A photosensitive polyimide using an alkaline aqueous solution as a developer

Compared with the nonphotosensitive polyimide, the photosensitive polyimide has become very important in the simplification of the patterning process. Its importance has prompted the development of a new type of photosensitive polyimide, using an alkaline aqueous solution as a developer. This photosensitive polyimide allows the formation of 40-μm-square via-holes in a film with a thickness of 15 μm and exhibits excellent physical properties after curing.     

Effect of supplementary cementitious materials (binder type) on the pore solution chemistry and the corrosion of steel in alkaline environments

The pore solution compositions of paste samples produced with Ordinary Portland Cement (PC), slag 25%, 50% and 75%, fly ash 30%, condensed silica fume (SF) 7%, and a ternary blend of 50% PC, 43% slag and 7% SF were determined. Not only are there significant variations in the concentration of the major cations and anions but also, and equally important from the perspective of development of the passivity of steel in solution, in the level of dissolved oxygen and redox potential.Further, the impact of changes in the pore solution chemistry of cement pastes with SCMs on the passivation and corrosion of steel was investigated with mild steel in simulated pore solutions (SPS). Sulphides and thiosulphates, typically found in slag bearing pastes, appeared to reduce the chloride threshold concentration and increase the rate of corrosion in SPS, which has potential implication for the long term performance of reinforced concrete structures.     

Effect of calcium to silica ratio on the synthesis of calcium silicate hydrate in high alkaline desilication solution

High alkaline desilication solution (DSS), a high volume byproduct from the pretreatment of high-alumina fly ash, was used as low-cost mother liquor for the synthesis of calcium silicate hydrate (C-S-H). Through the combined analysis of X-ray diffraction, thermogravimetric analysis, X-ray fluorescence, ²⁹Si MAS NMR, and Brunauer-Emmett-Teller, the relationship between chemical composition and structure of C-S-H synthesized under Ca/Si of 0.83:1 to 2.0:1 was investigated. Silicon conversion and yield of product have a positive correlation with Ca/Si. Sodium uptake in C-S-H is inhibited as Ca/Si increases. The formation of sodium in C-S-H transfers from “bound Na” to “mobile Na” and aluminum from tetrahedrally coordinated Al (IV) to octahedrally coordinated Al (VI). The increase of Ca/Si leads to shortening of silicate chain and formation of more dimers, which causes more water bound in C-S-H. The mechanism of calcium addition on silicate chain obtained from DFT calculation primarily results from more interlayer calcium occurrence to affect bridging tetrahedron and cationic bounding states reorganization. Reasonable control for Ca/Si momentously contributes to the adjustment for composition and structure of C-S-H synthesized in DSS.     

A new rapid titration method for determining the halogen ratio of Wijs solution and of iodine monochloride

The free iodine in Wijs solution is titrated directly, in strong hydrochloric acid solution, with standard potassium iodate solution. From this titration and the usual sodium thiosulfate titration for total halogen, the iodine/chlorine ratio is calculated. Results agree closely with those obtained by the longer chlorine-water method of Lopes. The halogen ratio of reagent grade iodine monochloride, a convenient material from which to prepare Wijs reagent directly, is also determined by the new titration method.     

Assessing coal pitch as a binder in anode production

The influence of various factors on the quality of anodes in aluminum production is analyzed. At present, no uniform approach permits the identification of a relation between the binder quality and the subsequent transformation of the pitch-coke composite in heat treatment. Measurable quality characteristics of the anodes used in aluminum production are considered. In selecting the optimum fluidity of the pitch and monitoring its variation at different temperatures, the determination of the dynamic viscosity is the most promising approach. The dynamic viscosity, which is the inverse of the fluidity, permits more reliable identification of the suppliers whose pitch is of the required quality. Introduction of a parameter such as the molecular-mass composition of the pitch in the corresponding standard is proposed.     

Application of gelatin as a binder for the sulfur cathode in lithium-sulfur batteries

Gelatin, a natural biological macromolecule, was successfully used as a new binder in place of poly(ethylene oxide) (PEO) in the fabrication of the sulfur cathode in lithium-sulfur batteries. The structure and electrochemical performance of the two types of sulfur cathodes, with gelatin and PEO as binders, respectively, were compared in 1 M LiClO₄ DME/DOL (V/V = 1/1) electrolyte. The results showed that the gelatin binder had multifunctional effects on the sulfur cathode: it not only functioned as a highly adhesive agent and an effective dispersion agent for the cathode materials, but also an electrochemically stable binder. The gelatin binder-sulfur cathode achieved a high initial capacity of 1132 mAh g⁻¹, and remained at a reversible capacity of 408 mAh g⁻¹ after 50 cycles, all of which were better than with the PEO binder-sulfur cathode under the same conditions.     

Effects of metakaolin, water/binder ratio and interfacial transition zones on the microhardness of cement mortars

Variations in the microhardness of the hydrated cement matrix component of model mortars have been investigated as functions of the distance from the aggregate surfaces for specimens in which the binder was Portland cement or a blend of Portland cement and metakaolin.Microhardness measurements were made using a Knoop indenter at distances of up to 120 μm from the aggregate. The microhardnesses of the paste-aggregate interfacial transition zones (ITZs) were found to be between 14% and 22% lower than those of the corresponding bulk cement pastes at the lower water/binder ratios investigated, i.e. 0.4 and 0.5 for samples prepared with Portland cement and 0.4 for samples prepared with a binder comprising Portland cement and metakaolin.Metakaolin increased the mean microhardness of specimens prepared at the higher water/binder ratios of 0.5 and 0.6 by 13% and 54%, respectively.     

Reactions of hydrogen peroxide on a silver electrode in alkaline solution

Reactions with hydrogen peroxide on silver in alkaline solutions with H₂O₂ concentration 5 × 10^?7 mol/ml have been studied with the ring-disk electrode. The amount of oxygen formed on the disk as the result of catalytic decomposition of hydrogen peroxide and its oxidation was established on the ring-electrode made from pyrographite. The rate constants of H₂O₂ electrochemical reduction (k₃), its oxidation (k′₂) and catalytic decomposition (k₄) and their dependence on potential have been evaluated. The constant k₄ scarcely depends on potential; it is ca 10^?2 cm/s.     

A study of Mo-modified Pd/MWCNT catalysts for ethanol oxidation in the alkaline solution

The effect of the modification of Pd-based electrocatalysts by molybdenum on the catalytic performance toward ethanol oxidation in the alkaline solution is investigated. The results indicate that the molybdenum oxide/hydroxide assists in the uniform distribution of Pd nanoparticles on the surface of the carbon support. The catalytic performance of the Mo-modified Pd/MWCNT catalyst is largely dependent on the temperature at which the molybdenum oxide/hydroxide is heat-treated. The catalyst prepared from the molybdenum oxide/hydroxide heat-treated at 350 °C has the highest catalytic activity and the best poison resistance. X-ray photoelectron spectroscopy results reveal that there is an interaction between Pd and Mo in Mo-modified Pd/MWCNT catalysts. The moderately dehydrated and oxidized molybdenum oxide/hydroxide has the strongest effect on promoting the catalytic activity and the poison resistance of Pd-based nanocatalysts for ethanol oxidation.     

Alkaline activation of the donbass coals of different ranks

The effect of the rank of coal (C ^daf = 80?95.2%) on the yield and characteristics of activated carbons prepared under the conditions of alkaline activation (800°C, 1 h, Ar) at KOH/coal ratios of 1 g/g was studied. Under these conditions, the ability of coals to form porous materials decreased in the metamorphic series. Grade D coal (C ^daf = 80%) exhibited a maximum activation ability to form a material with S _BET = 1560 m²/g, V _Σ = 0.71 cm³/g, and V _mi = 0.51 cm³/g. A minimum activation ability was found in anthracite (C ^daf = 95.2%), which forms activated carbon with poorly developed porosity (S _BET = 306 m²/g, V _Σ = 0.15 cm³/g, and V _mi = 0.11 cm³/g).     

A study of RuO2 as an electrocatalyst for hydrogen evolution in alkaline solution

The hydrogen evolution reaction (HER) on RuO₂ coated nickel electrodes was investigated by d.c. polarization studies and a.c. impedance measurements in alkaline solution. The electroactive RuO₂ coatings were prepared by thermal decomposition of a RuCl₃ solution at 450°C in air. The real surface area of the cathodes was estimated from cyclic voltammetric measurements and from the double layer capacitance (evaluated by impedance measurements). A mechanism for the HER has been proposed involving two steps (Volmer and Heyrovsky reactions). The rate constants of the forward and backward reactions of these two steps have been estimated by a nonlinear fitting procedure.     

Study of the hydrogen absorption in Pd in alkaline solution

Hydrogen adsorption/absorption in palladium thin deposits on gold electrode, in 0.1 M NaOH solution, was studied. The contributions of adsorption and absorption to the total charge of hydrogen are separated from the total isotherms at different deposit thicknesses. The adsorbed hydrogen charge increases to a plateau of ∼73.5 μC cm⁻², which corresponds to the surface coverage ratio by adsorbed hydrogen of 0.36. The absorbed hydrogen charge agreed with that obtained from the permeation experiments at 50 μm Pd foil, at potentials between +100 and +300 mV vs. RHE. EIS was carried out at thin Pd deposits. The kinetics of hydrogen sorption is slower in alkaline solutions than in acids and the isotherms are shifted towards more negative potentials.